Re: [PATCH 1/8] drm/dp: add drm_dp_128b132b_read_aux_rd_interval()

["Ville Syrjälä" <ville.syrjala@linux.intel.com>]

On Tue, Jan 25, 2022 at 07:03:39PM +0200, Jani Nikula wrote:
> The DP 2.0 errata changes DP_128B132B_TRAINING_AUX_RD_INTERVAL (DPCD
> 0x2216) completely. Add a new function to read that. Follow-up will need
> to clean up existing functions.
> 
> v2: fix reversed interpretation of bit 7 meaning (Uma)
> 
> Cc: Uma Shankar <uma.shankar@intel.com>
> Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
> Signed-off-by: Jani Nikula <jani.nikula@intel.com>

Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>

> ---
>  drivers/gpu/drm/dp/drm_dp.c    | 20 ++++++++++++++++++++
>  include/drm/dp/drm_dp_helper.h |  3 +++
>  2 files changed, 23 insertions(+)
> 
> diff --git a/drivers/gpu/drm/dp/drm_dp.c b/drivers/gpu/drm/dp/drm_dp.c
> index 6d43325acca5..52c6da510142 100644
> --- a/drivers/gpu/drm/dp/drm_dp.c
> +++ b/drivers/gpu/drm/dp/drm_dp.c
> @@ -281,6 +281,26 @@ int drm_dp_read_channel_eq_delay(struct drm_dp_aux *aux, const u8 dpcd[DP_RECEIV
>  }
>  EXPORT_SYMBOL(drm_dp_read_channel_eq_delay);
>  
> +/* Per DP 2.0 Errata */
> +int drm_dp_128b132b_read_aux_rd_interval(struct drm_dp_aux *aux)
> +{
> +	int unit;
> +	u8 val;
> +
> +	if (drm_dp_dpcd_readb(aux, DP_128B132B_TRAINING_AUX_RD_INTERVAL, &val) != 1) {
> +		drm_err(aux->drm_dev, "%s: failed rd interval read\n",
> +			aux->name);
> +		/* default to max */
> +		val = DP_128B132B_TRAINING_AUX_RD_INTERVAL_MASK;
> +	}
> +
> +	unit = (val & DP_128B132B_TRAINING_AUX_RD_INTERVAL_1MS_UNIT) ? 1 : 2;
> +	val &= DP_128B132B_TRAINING_AUX_RD_INTERVAL_MASK;
> +
> +	return (val + 1) * unit * 1000;
> +}
> +EXPORT_SYMBOL(drm_dp_128b132b_read_aux_rd_interval);
> +
>  void drm_dp_link_train_clock_recovery_delay(const struct drm_dp_aux *aux,
>  					    const u8 dpcd[DP_RECEIVER_CAP_SIZE])
>  {
> diff --git a/include/drm/dp/drm_dp_helper.h b/include/drm/dp/drm_dp_helper.h
> index 98d020835b49..aa73dfc817ff 100644
> --- a/include/drm/dp/drm_dp_helper.h
> +++ b/include/drm/dp/drm_dp_helper.h
> @@ -1112,6 +1112,7 @@ struct drm_panel;
>  # define DP_UHBR13_5                           (1 << 2)
>  
>  #define DP_128B132B_TRAINING_AUX_RD_INTERVAL                    0x2216 /* 2.0 */
> +# define DP_128B132B_TRAINING_AUX_RD_INTERVAL_1MS_UNIT          (1 << 7)
>  # define DP_128B132B_TRAINING_AUX_RD_INTERVAL_MASK              0x7f
>  # define DP_128B132B_TRAINING_AUX_RD_INTERVAL_400_US            0x00
>  # define DP_128B132B_TRAINING_AUX_RD_INTERVAL_4_MS              0x01
> @@ -1549,6 +1550,8 @@ void drm_dp_link_train_channel_eq_delay(const struct drm_dp_aux *aux,
>  void drm_dp_lttpr_link_train_channel_eq_delay(const struct drm_dp_aux *aux,
>  					      const u8 caps[DP_LTTPR_PHY_CAP_SIZE]);
>  
> +int drm_dp_128b132b_read_aux_rd_interval(struct drm_dp_aux *aux);
> +
>  u8 drm_dp_link_rate_to_bw_code(int link_rate);
>  int drm_dp_bw_code_to_link_rate(u8 link_bw);
>  
> -- 
> 2.30.2

-- 
Ville Syrjälä
Intel